The AT&T DSP1 was a pioneering digital signal processor (DSP) created by Bell Labs. The DSP1 started in 1977 with a Bell Labs study that recommended creating a large-scale integrated circuit for digital signal processing. It described a basic DSP architecture with multiplier/accumulator, addressing unit, and control; the I/O, data, and control memories were planned to be off-chip until large-scale integration could make a single chip implementation feasible. By October 1979 other Bell Labs groups began development using the DSP1, most notably as a key component in AT&T's 5ESS switch.